A recent report by consumer group Which? found food labels can be widely inaccurate.

Coupled with the recent Sudan I food scare, when it was discovered an illegal dye had been used in a variety of products, how can we ever be sure we can trust what's on the packet?

Food labelling is a complicated business. By the time a bottle of sauce or a ready-made chicken chow mein is on the shelf, can shoppers really make head or tail of the info on the label?

For instance, what does "best before" really mean? Does "light" really mean healthy? And what exactly are e-numbers?

Findings by the Food Standards Agency (FSA) also reveal consumers find food labels confusing - and many find them physically hard to read.

WHAT'S IN AN E?

E300 - vitamin C

E150a - caramel

E410 - locust bean gum

E621 - monosodium glutamate

E220 - sulphur dioxide

E9540 - saccharin

The FSA is calling for clearer labelling and has issued guidelines. It has suggested a 'traffic light' approach - green, eat plenty; amber, in moderation; red, eat sparingly.

It is also concerned with health claims made by manufacturers, which currently do not have to backed up by research.

The rules on labelling come from Europe, and among other things are dictated by the 'single market' competition rules.

For example, 'British' cannot be used to market a product.

Only on beef - because of the BSE crisis - and certain other fruit and vegetables must the country of origin be labelled.

Once food is processed - and this can mean as little as sprinkling salt on a lamb chop - what exactly can be called country of origin becomes a grey area.

If the salt was added in the UK, even if the lamb comes from elsewhere, then UK can go on the packet.

"It's rather misleading and a loophole we think must be closed," said Dr Helen Ferrier, food science adviser to the National Farmers' Union.

The Sudan I crisis saws hundreds of processed foods taken off the shelves

And, she said, from their members' point of view it was unfair competition.

"Generally, in the UK, we can't compete on price with most other places so there has to be something else that enables British farmers to market and get a reasonable price for their food.

"If people are looking are more than just price when they are choosing what to buy they have to be given the right information to choose what they want accurately."

But things are improving, said Michelle Smyth of Which?.

Until last year producers did not even have to include ingredients on their labels which were less than 25% of the overall product.

"Last year new EU rules came into force which means that apart from a few minor exceptions, all the ingredients must be listed on the label," she said.

WHAT IT MEANS

Best before date: From this point a product will not be harmful, but it may lost flavour and texture.

Lite or Light: The law does not define what this means, but manufacturers should really say why this is a 'healthier option'.

'Maintains healthy heart': Again there is no law specifically governing health claims. They do not have to be backed up by medical evidence, but it is illegal to be misleading.

Gluten free: Manufacturers are not required to say how much gluten is in a product, while products made from wheat with gluten taken out can claim to be gluten free. But, warns the FSA, it actually is impossible to take all gluten out of wheat.

This means a label should start with the ingredient most used, followed by the second, third, fourth...

"The situation now is a lot more positive," she said.

But Bev Wilson of Assured Food Standards, which runs the Red Tractor logo, said that unless you are prepared to take the raw ingredients and cook them at home, you were always going to run a food safety risk with processed food because it is such a complex business.

Processed food could not come with "cast iron guarantees" no matter how vigilant supermarkets are, she said.

"Food is ultimately a high-risk product," she said. "We live in a really fantastic choice driven environment. You can go into virtually any shop and buy anything from anywhere in the world.

"But you are moving away from the cast-iron guarantees that come from cooking a meal at home."

And of course additional information costs manufacturers, said the NFU's Helen Ferrier.

"If you want premium information you have to buy premium products," she said.